1. Field of the Invention
The present invention relates to a Lundell core type rotary electric machine having a rotor using Lundell-type pole cores.
2. Description of Related Art
A conventional vehicle alternating current generator is provided with a rotor using Lundell-type pole cores each of which has a plurality of claws, and generates electric power by rotating of the rotor. In recent years the electric load demands placed on vehicle electric systems have increased. Thus, the output power requirements of vehicle alternating current generators have increased. In some known generators, in order to increase power output permanent magnets magnetized in a direction diminishing magnetic flux leakage are inserted between the claws of the pole cores. For example, JP-A 7-312854, 3-150055 (U.S. Pat. No. 4,959,577), and 61-85045, disclose AC generator rotors having permanent magnets magnetized in a direction diminishing magnetic flux leakage are inserted between the claws of the pole cores. Since a plurality of separate permanent magnets are separately inserted between the claws of the pole cores in the rotor of the alternating current generator, the rotor is not easy to assemble.
JP-A 7-123664 (U.S. Pat. No. 5,483,116) and 3-265450 disclose an improved device which is easier to assemble. In the rotor of the alternating current generator disclosed in JP-A 7-123664, sixteen permanent magnets are inserted into a magnet holding member made of resin and spirally wound in the shape of a crown. The magnet holding member and the inserted permanent magnets are engaged using collars formed between the claws of the pole cores or by making the cross section of the magnet holding member in the direction of the rotation a trapezoidal shape, whereby the rotor is assembled into the magnet holding member together with the permanent magnets. In the rotor of the alternating current generator disclosed in JP-A 3-265450, the permanent magnets are arranged in the recesses which are formed on the inner peripheral side of a generally cylindrical non-magnetic ring filling the gaps between the claws of the pole cores and the rotor is assembled in the state that the permanent magnets are arranged in the non-magnetic ring.
In the magnet holding member used in the rotor disclosed in JP-A 7-123664 and the non-magnetic ring used in the rotor disclosed in JP-A 3-265450, the outer peripheral shape thereof must be matched with the shape of the inside surface and the shape of the side surface of the claws. If manufacturing errors in dimension of the pole cores or the magnets or in assembling the pole cores are not tolerable, it is likely that unnecessary stress is exerted on the permanent magnets and that the permanent magnets are cracked or chipped at the worst case, which results in a reduction in the output power of the alternating current generator, a breakage of the stator winding, or the like.
Moreover, the magnet holding member or the non-magnetic ring has a complicated shape and therefore it is not easy to form it from a non-magnetic material such as resin. The magnet holding member disclosed in JP-A 7-123664, for example, can not be easily formed by using two-way dies resulting in an increase of manufacturing cost.